Fine finishing of ground DOE lens of synthetic silica by magnetic field-assisted polishing

Needs of micro structured optical components are increasing in the astronomical space telescope. In the space having extremely large temperature differences, a diffractive optical element (DOE) lens is very effective in reducing the thermal chromatic aberration due to the thermal expansion. In order to finish the ground DOE lens of synthetic silica, a magnetic field-assisted polishing is proposed. In the experiments, DOE lens ground by the sharp edged diamond wheel is finished by the magnetic field-assisted polishing. By the grinding and polishing test, changes of form deviation profiles and surface roughness profiles are evaluated and feasibility is tested.